I preferred Eliminator and Frogbot to the Reaper bot because they were simply a little less perfect in how they played. Reaper had a habit of dominating routes and circle strafing with deadly precision, which just wasn't fun.

It kind of just depends on what the player likes, and the context.

If the enemy is supposed to be a super smart wizard, it'll feel stupid if it behaves in a dumb way.

Bots can't be too smart or they won't be fun is true statement of all gaming automation, not just bots.

Left 4 Dead feels great to play because the "AI director" chooses what happens next based on how and what the co-op team is doing. It's programmed to be both merciful and unfair, as appropriate. That, tuned right, has you "riding the edge" though the whole experience.

(I guess in the future, game studios will use ML instead of manually-tuned rules and heuristics, for that balance.)